The present invention relates to an apparatus for the coding or display, or simultaneous coding and display, of graphical information, more particularly of graphical data composed of nodes and links between these nodes, each node being capable of identification by at least one alphanumeric character and each link being capable of identification by its nature and its direction.
Apparatus of this type is already known for coding and simultaneous display of chemical formulae of the structural type. Because of the extremely high number of identified chemical compounds, it has been found necessary to undertake systematic recording of their formulae in coded form. The coded formula is transcribed on a record medium, such as a perforated card, perforated tape or magnetic tape, compatible with a data processing installation in order to permit later exploitation of the recorded formulae by computer, especially for documentary research operations. It is essential to check visually the accuracy of the coded formula and, preferably the coding and display of the formula take place simultaneously. Two types of apparatus are at present used for this purpose.
Apparatus of the first type comprises special typewriting machines with which a structural chemical formula to be coded is simultaneously reproduced on a paper sheet and on a magnetic tape or perforated tape. The printed result on the sheet allows visual verification and the magnetic tape or perforated tape is later read by a computer and the recorded data are used as a basis for the elaboration of the code. The keyboard of these typewriting machines comprises all the keys necessary for the reproduction of the particular symbols of these chemical formulae; in particular, the bonds are represented by vertical, horizontal or oblique dashes. In addition, the elementary operations such as spacing, return, line spacing which, although effected on the keyboard do not result in a print on paper, are recorded on the magnetic tape or perforated tape. Such apparatus has many disadvantages; in particular, errors which occur when the formula is typed cannot be corrected, the positioning of the carriage and the roller require relatively long mechanical displacements and the recording on magnetic tape or perforated tape must be processed by computer to permit its later exploitation in an information centre.
Apparatus of the second type requires a computer coupled on the one hand to a special keyboard similar to that of apparatus of the first type, and on the other hand to a cathode ray system for the display. Utilisation of this type of installation requires the preparation of a special program which first interprets the operation at the keyboard and then derives the elements to be coded and the image to be displayed. In addition to the high cost of their use, such installations require too long a processing time for the data to permit a sufficiently rapid scanning of the cathode ray tube screen to permit the provision on the screen of an image acceptable and not troublesome to an operator at the visual level. Although this would complicate the installation even more, one might thus be led to provide an intermediate data record medium, such as a video tape or disc on which the graphic data is recorded in analogue form, which data may then be displayed on the screen by reading this record medium.